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Topflight boffins say they may be able to plumb the secrets of silently-flying owls and use them to make all sorts of wing and propeller machinery - planes, helicopters, wind turbines, even submarines - much quieter than they are today.

"Owls possess no fewer than three distinct physical attributes that are thought to contribute to their silent flight capability: a comb of stiff feathers along the leading edge of the wing; a flexible fringe a the trailing edge of the wing; and a soft, downy material distributed on the top of the wing," explains Justin Jaworski, engineering prof at Lehigh uni in Pennsylvania.

These crafty appurtenances let hunting owls plunge down out of the night sky in complete silence, the better to surprise their prey. But Jaworski and his colleague Nigel Peake (of Blighty's Cambridge uni) believe that similar methods could practically be applied to various kinds of wings and blades used in helicopters, wind turbines, aeroplanes and warships.

"The dominant edge-noise source could be effectively eliminated with properly tuned porous or elastic edge properties, which implies that that the noise signature from the wing can then be dictated by otherwise minor noise mechanisms such as the 'roughness' of the wing surface ...

"If the noise-reduction mechanism of the owl down can be established, there may be far-reaching implications to the design of novel sound-absorbing liners, the use of flexible roughness to affect trailing-edge noise and vibrations for aircraft and wind turbines, and the mitigation of underwater noise from naval vessels," Jaworski goes on to say.

If the men are right and their theories can be turned into practical technology, a lot of fictional aspirations might come true. The "whisper mode" often featured on the black helicopters of the US secret state* - and a blue chopper of the LA cops, in celluloid epic Blue Thunder - might become a reality. Silenced propeller blades might permit a truly quiet submarine, Hunt for Red October style.

Quiet fan or rotor blades would also remove one of the main barriers facing the long-awaited flying car - that of noise levels. Some people think that an actual vertical-lift, all-singing-all-dancing aircar can now be built, and that its power system can be in large part electric and so much quieter than normal aircraft.

But so far nobody has explained how such craft would ever get permission to fly over (still less, land and take off in) urban areas, when their thundering blades would deafen everyone for streets around. Now, perhaps, a solution may be at hand - and one more obstacle ahead of the proper Jetsons-style flying car may be about to topple. ®

Bootnote

*There really are such aircraft, but they probably don't exactly whisper: it's more a matter of shouting a bit less loudly.